wow thats o clever, is that like two prop shafts there then i see too ?
As Phil said the big shaft is the main prop, and the smaller one is the shaft to the front diff / transfer box.
Im guessing all the 4WD torque bias work is dont at the gear box, and not the diffs though, else why run a seperate shaft under the car, and why the need for a shaft unless its running at a different speed to the main prop.
Pretty clever shit